1. Field of the Invention
This document relates to a stereoscopic image display and an alignment method thereof.
2. Related Art
An image display device implements 3D images using a stereoscopic technique and an autostereoscopic technique.
The stereoscopic technique uses binocular parallax images which produce large stereoscopic effects, and may or may not have a corresponding set of lenses or eyeglasses for viewing by the user. In the type of system using eyeglasses, binocular parallax images are displayed on a direct view display panel or by a projector by changing polarization directions. Alternatively, using temporal division, polarization eyeglasses or liquid crystal shutter eyeglasses may be used to implement stereoscopic images. In the type of system not using eyeglasses, the stereoscopic images are implemented by dividing optical axes of binocular parallax images, where optical plates, such as parallax barriers, are provided at front and rear surfaces of a display panel.
To mass-produce the stereoscopic image display devices, it is necessary to efficiently align a display device and a 3D filter, which is disposed on the display device and divides light from the display device into light corresponding to left eye images and light corresponding to right eye images.
A method of aligning a parallax barrier with a display panel has been proposed in Korean Patent No. 10-0709728, where separate eyeglasses are not used. In this method, as shown in FIG. 1, two cameras CAM1 and CAM2 disposed at a predetermined distance from the display panel 1 and from the parallax barrier 2, take stereoscopic images displayed on the display panel 1. The display panel 1 and the parallax barrier 2 are repeatedly realigned while checking the division state of left eye images and right eye images until reaching a predetermined alignment reference state.
However, in a method of aligning a display panel with a 3D filter by a worker who views images displayed on the display panel based on luminosity, or in a method that determines whether or not stereoscopic images are divided over a predetermined reference value in a system using two cameras, power data and test pattern data must be provided to the display panel so as to display the images. Therefore, using such related art alignment techniques, it is difficult to numerically quantify the degree of alignment or misalignment, equipment cost is high, and productivity is low.
In a known method of aligning a display panel with a 3D filter in the eyeglass type stereoscopic image display device, a worker wears polarization eyeglasses, drives a display panel placed at a certain distance, determines an alignment degree between the display panel and the 3D filter through luminosity, and repeats the above-described operation until images displayed on the display panel are properly viewed. The assignee of the present application has proposed, in Korean Patent No. 10-0939214, a alignment system and method of stereoscopic image display devices which can automatically align the 3D filter with the display panel in the eyeglass type and solve the problems disclosed in Korean Patent No. 10-0709728. In this method, alignment marks are formed in a display panel and a 3D filter, the alignment marks are checked by a vision system, and thereby the display panel and the 3D filter can be aligned with each other without driving the display panel. Also, an alignment state can be quantified by checking an alignment state of the alignment marks.
The 3D filter may have a known tolerance or variation. In this case, because an accumulated error increases as the distance increase from the alignment reference positions (alignment marks) during the alignment of the display panel with the 3D filter, an alignment error accumulates. As a result, up and down viewing angles in the stereoscopic image display device may be narrowed due to the tolerance or variation of the 3D filter.